This invention relates to the art of infusion pumps. In particular, the invention relates to a method and apparatus for allowing rapid deflation of a pressure infusion bladder.
The use of infusion devices for supply of intravenous fluids to patients is well known. As well, it is known to provide these intravenous fluids under pressure to increase the flow rate. The pressure has been provided by several techniques, one of which is to engage a bag containing the fluid with an inflatable bladder. The bladder is inflated by air from a compressor, or another source of pressurized gas, which is connected to the bladder through a control valve.
It is also known to allow deflation of the bladder by a control valve that can be placed in a position whereby it vents the bladder to the atmosphere, such as is shown in U.S. Pat. Nos. 3,640,276 and 4,430,078. It is also known to provide rapid deflation of a bladder by a venturi that produces a lower pressure for pumping the air out of the bladder.
A problem with prior control valves has been to combine rapid deflation, ease of operation, and low manufacturing cost.
In accordance with the invention, a pressure infusion system includes an inflatable bladder for engaging a flexible bag of physiological fluids, a pump for supplying air under pressure, and a valve for controlling both supply of the pressurized air to the bladder and rapid exit of air from the bladder.
One feature of the invention is the use of a large-bore supply tube connecting the outlet of the control valve to the bladder. The diameter of this tube is much larger than is required to supply the bladder with air, and is made large because the control valve also allows deflation of the bladder through the tube. The increased bore size allows the bladder to deflate very rapidly without further assistance. Thus, the control valve of the invention includes an inlet for receiving air from a pressure pump, an outlet for transmitting air under pressure to the bladder, and a discharge port for allowing rapid discharge of the bladder. In the preferred embodiment, the valve comprises a body portion having a docking port and an outlet port. The body receives a toggle element that is mounted for pivotal movement between these two ports. The toggle includes an inlet port and a channel for communication with the docking port or the outlet port, depending on whether the toggle is in the inflate or deflate position.
When the toggle is in the inflate position the channel is in communication with the outlet port, and air under pressure is supplied to the bladder through the large bore tube. When the toggle is in the deflate position, the channel is in communication with the docking port, and the outlet port is open to the atmosphere. Thus, in the deflate position, the air in the bladder is rapidly discharged to the atmosphere to allow a full bag of fluids to be installed easily.
The invention also includes a method of inflating and deflating an expandable bladder in conjunction with pressurizing a flexible bag of physiological fluid by inflating the expandable bladder by introducing pressurized fluid into the expandable bag first through an inlet channel having a first cross sectional area and then through a supply tube in communication with the expandable bladder. The bladder can then be deflated by bypassing the inlet channel to release the pressurized fluid first through the supply tube and then through an outlet exposed by the bypassing of the inlet channel, the outlet having a second cross sectional area greater then the first cross sectional area of the inlet channel.
It will be appreciated that the valve of the invention is unique in that the inlet port is quite small relative to the outlet port. Similarly, the tubing connecting the air pump to the inlet is much smaller than the supply tube connecting the valve to the bladder.
The system of the invention is preferably implemented by mounting the control valve on the base of the device such that the toggle is easily accessed by an operator. This position is such that the operator can easily move the toggle between inflate and discharge positions while opening or closing the door to the device and exchanging the fluid bags.